1. Technical Field
The present invention is directed to controlling actuation of a vehicle passenger restraint system and is particularly directed to evaluating a crash condition with different crash evaluation algorithms for determining whether the crash condition is sufficient to warrant actuation of the restraint system.
2. Prior Art
Actuatable passenger restraint systems for vehicles are well known in the art. Such systems are used to sense a crash condition and, in response to such a condition, to actuate an airbag or lock a seat belt or actuate a pretensioner for a seat belt retractor.
The U.S. Pat. No. 3,870,894 to U. Brede et al. discloses an actuatable passenger restraint system employing an electrical transducer for providing an electrical signal indicative of a deployment condition, such as vehicle deceleration, for use in actuating such a restraint system. The transducer employed is a piezoelectric transducer operating as an accelerometer and provides an output signal having a value indicative of vehicle deceleration. That signal is evaluated in accordance with a particular crash evaluation algorithm. The crash evaluation algorithm involves integrating the output signal to provide an integrated signal representative of velocity. When the integrated signal reaches a predetermined value, a trigger signal is provided for actuating the restraint system.
The U.S. Pat. No. 3,911,391 to M. Held et al. is similar to that of Brede et al., but discloses a second crash evaluation algorithm. The second evaluation algorithm includes performing a double integration of the output signal of the accelerometer such that the integrated signal represents displacement. Once the integrated signal representative of displacement reaches a predetermined value, a trigger signal is provided for actuating the restraint system.
Brede et al. discloses a crash evaluation circuit employing a velocity algorithm. Held et al. discloses a crash evaluation circuit employing a displacement algorithm. However, Brede et al. and Held et al. have no provision for evaluating a crash condition with two or more different crash evaluation algorithms to determine whether the crash condition is sufficient to warrant actuation of the restraint system.
The U.S. Pat. No. 3,762,495 to Usui et al. discloses an apparatus for actuating a passenger restraint system in a vehicle which relies, in part, for its operation on sensing whether the rate of change of vehicle deceleration, i.e., jerk, exceeds a jerk threshold level. This may be referred to as a third crash evaluation circuit employing a jerk algorithm. Usui et al. also discloses an apparatus for actuating a passenger restraint system in a vehicle which relies, in part, for its operation on sensing whether the level of vehicle deceleration exceeds a deceleration threshold level. This may be considered as a crash evaluation circuit employing a deceleration algorithm. Moreover, Usui et al. discloses combining the two evaluation circuits so that both algorithms are concurrently employed. Each evaluation circuit produces an output signal when its algorithm determines that the restraint system should be deployed. When both evaluation circuits concurrently provide such an output signal, then a trigger signal is provided for actuating the restraint system. This may be considered as a system that requires a unanimous vote by the evaluation circuits, wherein each evaluation circuit has one vote.
Usui et al. has no provision for determining which of the two crash evaluation circuits is the expert in evaluating a crash condition under consideration and giving extra weight to that circuit's evaluation of the crash condition in deciding whether to actuate the vehicle restraint system.